The present invention relates to a device for qualification of products containing volatile substances forming an analyte, that comprises a measuring unit with a measuring enclosure and an electronic circuit for analysis to define the characteristics of the analyte, a pumping system to make a vacuum inside the enclosure, a sampling chamber in which the analyte is introduced and a capillary to connect the sampling chamber to the enclosure.
Such a device is particularly used to identify fragrant particles. That is why it is sometimes called xe2x80x9cartificial nosexe2x80x9d. It finds applications in food or perfume industry for example and allows to ensure, by the analysis of fragrant molecules, that the quality of manufactured products stays in the limits of the required standard. It can be used particularly to highlight a modification of the characteristics of certain basic components or an evolution of one or another step of a manufacturing process.
To this effect, a defined quantity of product to control is sampled, in a programmed way, and confined in a vial with given dimensions, constant for a series of measurements. The vial is chosen to let a non filled space that contains the analyte, after having reached an equilibrium, made of volatile substances representative of the product.
In the devices actually used for such operations, the analyte is often characterized with a gas chromatograph. It is done by introducing the analyte in a chamber connected to a detection system with a column filled with particular material. The choice of that material and the operating conditions allow to induce different migration speeds for each substance making the analyte. A carrier gas, slightly pressurized, guarantees the carrying of these substances.
So the arrival time at the detector varies with the characteristics of the molecules making the analyte. Thus it is possible to know the quality of a product according to the sequence and the density of molecules arriving to the detector. However, the information obtained that way doesn""t allow to identify the substances. It is generally enough to follow the evolution of the fingerprint left by the analyte after a measuring cycle.
To identify the substances, a mass or an infrared spectrometer has been added at the column outlet. Thus it is possible to have additional information on the chemical composition of the analyte.
The used mass spectrometer is generally chosen to be able to analyze the whole ion spectrum coming from the dissociation of the analyte molecules, that can have a molar mass up to 400 and more. Such spectrometers are expensive, delicate and sensitive to oxygen in its part responsible of the measurement, making them poorly adapted to the measurement of analytes commonly rich in air.
The Japanese patent 8""201""249 describes a device functioning without a chromatograph. It includes a chamber in which a sample is placed. This chamber is connected with a capillary to a mass spectrometer including a measuring enclosure. The chamber, the capillary and the enclosure are heated, not only to promote the odor release, but also to avoid their adsorption on the walls.
The use of the devices described above requires however some care, especially to ensure that the product previously measured doesn""t remain in the chamber, the enclosure or the column, for example adsorbed on the walls, what could falsify the next measurement. Thus it is necessary to do some heavy and expensive operations to guarantee the cleanness of these devices.
The main purpose of the present invention is to palliate this drawback and more especially to allow the realization of a device such as defined above, easy to use and capable to be automated.
To that effect, the invention concerns a device to qualify products containing volatile substances forming together an analyte, that comprises a measuring unit with a measuring enclosure and an electronic circuit for analysis to define the characteristics of the analyte, a pumping system to make a vacuum inside the enclosure, a sampling chamber in which the analyte is introduced and a capillary to connect said chamber to said enclosure, the sampling chamber of this device including:
a first inlet to introduce the analyte and fitted with a gastight cap,
a second inlet connected to a source of purge gas and fitted with a valve and
an outlet allowing the exhaust of the gas contained in the chamber and also fitted with a valve.
The device comprises moreover a transfer system to introduce the analyte into the sampling chamber and a command programmer for the analysis circuit, the transfer system and the valves, allowing to achieve sequentially the purge of the sampling chamber, the capillary and the enclosure, then the introduction of the analyte into the enclosure, and finally its analysis.
According to a first embodiment of the invention, the device is characterized by the fact that the programmer is set up in such a way that:
in a first phase, the valves of the second inlet and the outlet are open to let the purge gas go through as long as a significant number of analyte particles previously analyzed may remain in the chamber, the enclosure or the capillary,
in a second phase, the inlet valve is closed, preventing the penetration of the purge gas,
in a third phase, the transfer system is activated, to introduce the analyte to measure into the chamber,
in a fourth phase, the outlet valve is closed,
in a fifth phase, at least, the analysis apparatus defines the characteristics of the analyte passing from the chamber into the encosure,
in a sixth phase, the operation starts again at the first phase, as long as there are still other products to qualify.
According to another embodiment of the invention, the device comprises an adsorbing material on which the analyte is adsorbed.
In that case, preferably, the programmer is set up in such a way that:
in a first phase, the valves of the second inlet and the outlet are open to let the purge gas go through as long as a significant number of analyte particles previously analyzed may remain in the chamber, the enclosure or the capillary,
in a second phase, the inlet and outlet valves are closed quite simultaneously, preventing particularly the penetration of the purge gas,
in a third phase, the transfer system is activated, to introduce the analyte to measure into the chamber,
in a fourth phase, at least, the analysis apparatus defines the characteristics of the analyte passing from the chamber into the enclosure, and
in a fifth phase, the operation starts again at the first phase, as long as there are still other products to qualify.